Medical device delivery member with flexible stretch resistant distal portion

ABSTRACT

A delivery member is provided for delivering and deploying an intravascular medical device. The delivery member includes a flexible distal portion including a wound wire coil surrounded by a flexible sleeve and inhibited from extending lengthwise by a stretch resistant member positioned through the lumen of the coil. The delivery member can include hypotubes positioned on either side (distally and proximally) from the wound wire coil to which the stretch resistant member and the wound wire coil can be attached.

FIELD OF INVENTION

This invention generally relates to intravascular medical device systems that navigable through body vessels of a human subject. More particularly, this invention relates to delivery systems and delivery members for delivering and deploying an implantable medical device to a target location of a body vessel and methods of using the same.

BACKGROUND

The use of catheter delivery systems for positioning and deploying therapeutic devices, such as dilation balloons, stents and embolic coils, in the vasculature of the human body has become a standard procedure for treating endovascular diseases. It has been found that such devices are particularly useful in treating areas where traditional operational procedures are impossible or pose a great risk to the patient, for example in the treatment of aneurysms in cranial blood vessels. Due to the delicate tissue surrounding cranial blood vessels, e.g. brain tissue, it can be difficult and often risky to perform surgical procedures to treat defects of the cranial blood vessels. Advancements in catheter-based implant delivery systems have provided an alternative treatment in such cases. Some of the advantages of catheter delivery systems are that they provide methods for treating blood vessels by an approach that has been found to reduce the risk of trauma to the surrounding tissue, and they also allow for treatment of blood vessels that in the past would have been considered inoperable.

Typically, these procedures involve inserting a delivery catheter into the vasculature of a patient and guiding it through the vasculature to a predetermined delivery site. A vascular occlusion device, such as an embolic coil, can be attached to an implant engagement/deployment system (referred to herein equivalently as an “engagement system” or “deployment system”) at a distal end a of a delivery member (e.g. micro-catheter) which pushes the coil through the delivery catheter and out of the distal end of the delivery catheter into the delivery site. Example delivery members and engagement/deployment systems are described in U.S. patent application Ser. No. 15/850,993 and U.S. patent application Ser. No. 15/964,857 each incorporated herein by reference.

Some of the challenges that have been associated with properly executing such treatment procedures include ensuring the delivery member and engagement system remain in a stable position throughout a treatment. For example, in some aneurysm treatment applications, as the aneurysm becomes increasingly packed with embolic material, the delivery member can tend to shift due to increasing pushback from the embolic material being implanted. If the delivery member shifts during treatment, a physician may not be able to accurately control placement of embolic material and may choose to cease packing the aneurysm. In such an example, the aneurysm may not be sufficiently packed, which can lead to recanalization. Further, excessive movement or stretching of the delivery member and/or engagement system thereon can result in premature detachment of the embolic coil.

There is therefore a need for improved methods, devices, and systems to provide an implant delivery member and implant engagement system with increased stability.

SUMMARY

It is an object of the present invention to provide systems, devices, and methods to meet the above-stated needs. Generally, it is an object of the present invention to provide a delivery member for delivering and deploying an implantable medical device having a flexible distal portion.

Stiffness of the distal portion of the delivery member can cause the microcatheter used for delivery of the embolic material to pull back out of the aneurysm as the distal end of the delivery member is advanced through the tortuous distal anatomy. If the microcatheter pulls back while advancing the embolic material, the microcatheter may come out of the aneurysm and the physician may lose control of the embolic coil and not be able to accurately control placement of embolic material and may not be able to complete treatment.

Flexibility can be provided by incorporating a length of wound coil along the distal portion of the delivery member. The wound coil can be protected by a flexible polymer sleeve positioned around the outside of the coil. The wound coil can be inhibited from elongating by a stretch resistant tube affixed to hypotubes on either end of the wound coil.

An example delivery member for delivering an implantable medical device to a target location of a body vessel can include a distal hypotube, a support coil section, a proximal hypotube, a flexible sleeve covering the support coil section, and a stretch resistant member extending across the support coil section. The distal hypotube, support coil section, and proximal hypotube can form a contiguous tubular structure having a lumen therethrough. The flexible sleeve can cover some or all of the support coil section to prevent radial expansion of the support coil section and to promote the ability of the support coil section to slide through vasculature. The stretch resistant member can be affixed to the proximal hypotube and the distal hypotube, thereby extending across the entirety of the support coil section.

The delivery member can also include an engagement system that can move to engage and deploy the implantable medical device. The engagement system can include a loop wire and a pull wire. The loop wire can extend through an opening in the implantable medical device and the pull wire can be engaged to the loop wire, thereby engaging the engagement system to the implantable medical device. The pull wire can be positioned within the lumen of the delivery member and can be retracted proximally to disengage the loop wire. Once disengaged from the pull wire, the loop wire can be movable to retract from the opening in the implantable medical device, thereby deploying the implantable medical device.

At least a portion of the distal hypotube can be compressed and can elongate upon movement of the engagement system, when the engagement system is moved to deploy the implantable medical device.

The support coil section can include a non-radiopaque proximal coil, a non-radiopaque distal coil, and a radiopaque central coil positioned between the non-radiopaque coils.

The support coil section can be made from a wire wound to define a portion of the lumen of the delivery member. The wire from which the support coil is made can have a cross-sectional diameter measuring from about 0.8 mil to about 5 mil (about 20 nm to about 130 nm).

The flexible sleeve can include a polymer. The flexible sleeve can include additives to increase lubricity of the polymer.

The flexible sleeve can be affixed to the proximal hypotube and the distal hypotube. The flexible sleeve configured thusly can thereby cover the entirety of the coiled section and at least a portion of the proximal hypotube and/or at least a portion of the distal hypotube.

The stretch resistant member can be an extruded tube.

The support coil section and the distal hypotube can have a length measured from the proximal end of the support coil to the distal end of the distal hypotube that measures between about 30 cm and about 50 cm, or more specifically, about 40 cm.

The proximal hypotube can include a spiral cut portion near its distal end.

An example method for designing or constructing a delivery member such as the example above can include the steps of selecting a first hypotube and a second hypotube, forming a wire coil section between the two hypotubes, extending a stretch resistant member through the lumen of the wire coil section, affixing the stretch resistant member to the first and second hypotubes, selecting a flexible sleeve, covering the support coil section with the flexible sleeve, and attaching the implantable medical device to the distal end of the first hypotube such that the implantable medical device can be detached from the first hypotube during a treatment.

The step of forming the wire coil section can include forming a non-radiopaque proximal coil, forming a non-radiopaque distal coil, and forming a radiopaque central coil extending between the non-radiopaque proximal coil and non-radiopaque distal coil. Alternatively, the wire coil section need not include a radiopaque section. The step of forming the wire coil section can additionally or alternatively include selecting a wire having a diameter measuring about 0.8 mil to about 5 mil (about 20 nm to about 130 mm) and winding the wire to form the wire coil section and to define the lumen of the wire coil section.

The step of selecting the flexible sleeve can include selecting a polymer sleeve having additives to increase lubricity of the polymer.

The step of extending the stretch resistant member through the wire coil lumen can include extending a substantially tubular stretch resistant member through the wire coil lumen.

The step of attaching the implantable medical device to the first hypotube can include compressing the first hypotube and attaching the implantable medical device to the distal end of the compressed first hypotube.

The example method for designing or constructing a delivery member can further include positioning a loop wire within the lumen of the first hypotube and positioning a pull wire to extend through lumens of the first hypotube, wire coil section, and the second hypotube. The step of attaching the implantable medical device can additionally or alternatively include extending the loop wire through an opening in the implantable medical device and engaging the pull wire to a portion of the loop wire extended through the opening of the implantable medical device. The step of attaching the implantable medical device can additionally or alternatively include positioning the pull wire to extend proximally from a proximal end of the second hypotube.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further aspects of this invention are further discussed with reference to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating principles of the invention. The figures depict one or more implementations of the inventive devices, by way of example only, not by way of limitation.

FIG. 1 is an illustration of a cross section of a delivery member according to aspects of the present invention;

FIG. 2A is an illustration of a cross section of a flexible sleeve according to aspects of the present invention;

FIG. 2B is an illustration of a cross section of a stretch resistant tube according to aspects of the present invention;

FIG. 2C is an illustration of a cross section of a wire coil affixed to a distal hypotube and a proximal hypotube according to aspects of the present invention;

FIGS. 3A through 3D are illustrations of an engagement system illustrating a sequence for deploying an implant according to aspects of the present invention;

FIG. 4 is a flow diagram illustrating a method for designing or constructing a delivery member according to aspects of the present invention; and

FIG. 5 is a flow diagram illustrating a method for using a delivery system including an example delivery member according to aspects of the present invention.

DETAILED DESCRIPTION

During an intravascular treatment, for instance, an aneurysm occlusion treatment, lack of flexibility of a distal portion of a treatment device delivery member can cause the delivery member to pull back from the treatment site or otherwise move out of position while an implant or other medical treatment device is being placed in an aneurysm or other treatment site. A delivery member and engagement system having a more flexible distal portion can therefore provide a stable system for delivering medical devices in neurovascular anatomy in addition to other applications facing a similar challenge. Flexible structures, however can tend deform, extend, or expand when navigating tortuous anatomy. Deformation of the delivery member can inhibit the delivery member's ability to navigate to a treatment site and/or effectively deploy the medical device. Elongation of the delivery member can result in premature deployment of the medical device.

An object of the present invention is to provide a delivery member having a highly flexible distal portion that is stretch resistant and structurally stable throughout delivery and deployment of a medical treatment device. For ease of discussion, medical treatment devices are generally referred to herein as an “implant” although, as will be appreciated and understood by a person of ordinary skill in the art, aspects of the present invention can be applied to deliver and deploy medical treatment devices that are not left implanted.

According to the present invention, in some examples, the highly flexible distal portion of the delivery member can include a coiled wire, an outer sleeve, and an inner stretch resistant member. The coiled wire can be formed of a substantially linear wire that is wound in a coil shape and/or a hypotube that is laser cut in a spiral pattern. If the coiled wire is formed from a laser cut hypotube, the spiral can be absent interference cuts connecting windings in the coil so as to provide a more flexible coil. The outer sleeve can inhibit the coiled wire from deforming radially and/or provide a smooth surface against which vascular walls can slide during delivery of an implant. The stretch resistant member can inhibit elongation of the coiled wire during delivery of the implant. The combination of the coiled wire, outer sleeve, and stretch resistant member can therefore provide a distal portion of a delivery member having greater flexibility and greater stability than at least some known delivery members.

Turning to the figures, as illustrated in FIG. 1, an example delivery member 10 can include a proximal tube 100, a coiled section 200, a distal tube 300, a sleeve 500 surrounding the coiled section, and a stretch resistant member 600 within the lumen of the coiled section 200. The proximal tube 100 can extend a majority of the length of the delivery member 10 with the coiled section 200 and distal tube 300 forming a length sufficient to absorb a majority of push-back that can occur during placement of an implant at a treatment site. In some examples, the length can measure between about 30 cm and about 50 cm, or more specifically, about 40 cm. The proximal tube 100 can have a distal end 104 that is connected to a proximal end 202 of the coiled section 200, and the coiled section 200 can have a distal end 204 that is connected to a proximal end 302 of the distal coil 300.

FIG. 2A is a cross sectional view of the sleeve 500. FIG. 2B is a cross sectional view of the stretch resistant member 600. FIG. 2C is a cross sectional view of the assembled proximal tube 100, coiled section 200, and distal tube 300.

The coiled section 200 can be formed separately from the proximal hypotube 100 and/or the distal hypotube 300. The separately formed coiled section 200 can be affixed with welds 712, 714 or other appropriate attachment to the proximal tube 100 and/or the distal tube 300. Alternatively, or additionally, at least a portion of the coiled section can be formed from a spiral laser cut portion of a hypotube. A separately formed coiled section 200 can be made more flexible compared to a spiral cut tube by selecting a wire with a particular cross section (e.g. circular) with a particular diameter D, or by selecting a wire with material properties to increase flexibility. Conversely, a laser cut portion can be more easily fabricated by cutting a single hypotube to form the proximal tube 100, coiled section 200, and distal hypotube 300, reducing or eliminating welds 712, 714 or other attachments. In either case, the wire of the coil 200 can have a diameter D measuring within a range including about 0.8 mils and 5 mils (about 20 nm to about 130 nm).

The coiled section can be formed primarily of a non-radiopaque material such as steel and can include a radiopaque section 216 made of a radiopaque material such as platinum and/or tungsten. The radiopaque section 216 can be positioned between a proximal, non-radiopaque section of the coil 212 and a distal, non-radiopaque section of the coil 214. The radiopaque section 216 can be positioned a predetermined distance from a distal end 304 of the delivery member 10 so that a physician can readily visualize the placement of the distal portion of the delivery member during a treatment procedure. The proximal section 212, radiopaque section 216, and distal section 214 can be concentrically welded.

The coiled section 200 can be surrounded by a flexible sleeve or fused jacket 500, referred generically herein as a “sleeve”. The sleeve can inhibit the coil 200 from expanding radially and/or from engaging vascular walls during navigation. The sleeve 500 can include a polymer. The polymer can include additives to increase the lubricity of the sleeve 500 so that the sleeve can easily slide through a body vessel. As illustrated in FIG. 2A, the sleeve 500 can have a wall thickness T measuring within a range including about 0.5 mils and about 2 mils (about 0.01 mm to about 0.05 mm). The sleeve 500 can further be coated with a hydrophilic coating to further minimize friction during intravascular navigation. The sleeve 500 can be fused or glued to the coil 200, the proximal hypotube 100, and/or the distal hypotube 300.

The stretch resistant member 600 can be positioned to inhibit elongation of the coil 200 during intravascular navigation. The stretch resistant member 600 can include a tube sized to fit within the lumen 208 of the coil 200. The stretch resistant tube 600 can also be sized to extend through the entirety of the length of the coil 200, extend with a lumen 108 of the proximal tube 100 and within the lumen 308 of the distal coil 300. The stretch resistant member 600 can be attached to the proximal tube 100 and the distal tube 300 at adhesive joints 702, 704 or other appropriate attachment. The stretch resistant member 600 can remain unattached to the coiled section 200 such that the stretch resistant member 600 and coiled section 200 are able to move independently from each other to some extent.

The delivery member 10 can include a mechanical engagement system for engaging a medical treatment device during delivery to a treatment site that can be actuated mechanically to deploy the treatment device. Mechanically actuated engagement systems often include one or more inner elongated members or pull wires extending through the delivery member that can be manipulated at the proximal end by a physician to deploy a medical treatment device. Such a wire or inner elongated member is referred to herein generically as a “pull wire”.

FIGS. 3A through 3D illustrate the delivery member 10 including a mechanical engagement system including a pull wire 140 and a loop wire 400 that can be positioned to secure an implant or other medical treatment device to the delivery member 10 and can be moved to release the medical treatment device from the delivery member 10. The loop wire 400 can be affixed to the distal tube 300 with a weld 408 or other or other suitable attachment (see FIG. 1). The stretch resistant member 600 can be sized to allow a pull wire 140 to pass through the lumens 108, 208, 308 of the proximal tube 100, coiled section 200, and distal tube 300. For instance, the stretch resistant member 600 can be tubular, having a lumen therethrough, and the pull wire 140 can extend through the lumen of the tubular stretch resistant member 600. During manufacture of the stretch resistant member 600, the stretch resistant member 600 can be extruded over the pull wire 140.

The combination of the coil 200, sleeve 500, and stretch resistant member 600 can provide a highly flexible distal portion of a delivery member 10 suitable for navigating tortuous anatomy, including neurovascular blood vessels. The stretch resistant member 600 can support the coil 200 to prevent the coil 200 from significantly extending during navigation of a blood vessel, thereby reducing tension on a pull wire 140 extending therethrough and reducing the likelihood of premature deployment of an attached medical treatment device.

The proximal tube 100 can include a flexible section 106 having material removed to increase flexibility of the flexible section 106. The flexible section 106 can be cut in a spiral pattern. The spiral pattern of the flexible section 106 can lack interference cuts connecting windings within the spiral. The stretch resistant member 600 can extend through the flexible section 106 and be attached to the proximal tube 100 in the proximal direction from the flexible section 106. The stretch resistant member 600 can thereby inhibit elongation of the flexible section 106 of the proximal tube 100 and coiled section 200. The sleeve 500 can cover at least a portion of the flexible section 106 to inhibit deformation of the flexible section and/or reduce friction with vasculature and the flexible section 106 during intravascular navigation. In some examples, the sleeve 500 can cover about 10 cm of the proximal tube 100 approximate and/or including the distal end 104 of the proximal tube 100.

The distal tube 300 can include a compressible portion 306. The compressible portion 306 can be axially adjustable between an elongated condition and a compressed condition. The compressed portion 306 can be formed from a spiral-cut portion of the tube 300, formed by a laser cutting operation. Additionally, or alternatively, the compressible portion can be formed of a wound wire, spiral ribbon, or other arrangement allowing axial adjustment according to the present invention. Preferably, the compressible portion 306 is in the elongated condition at rest and automatically or resiliently returns to the elongated condition from a compressed condition, unless otherwise constrained.

FIGS. 3A-3D, illustrate the detachment of the medical device 12 using a mechanical engagement/deployment system. FIG. 3A illustrates the engagement system 140, 400 locked into the locking portion 18 of the medical device 12. The compressible portion 306 of the distal tube 300 can be compressed and the loop wire 400 opening 405 at a distal end 404 of the loop wire 400 can be placed through the locking portion 18. When the pull wire 140 is put through the opening 405 the medical device 12 is now secure. FIG. 3B illustrates the pull wire 140 being drawn proximally to begin the release sequence for the medical device 12. FIG. 3C illustrates the instant the pull wire 140 exits the opening 405 and is pulled free of the loop wire 400. The distal end 404 of the loop wire 400 falls away and exits the locking portion 18. As can be seen, there is now nothing holding the medical device 12 to the detachment system 10. FIG. 3D illustrates the end of the release sequence. Here, the compressible portion 306 has extended/returned to its original shape and “sprung” forward. An elastic force E is imparted by the distal end 304 of the distal tube 300 to the medical device 12 to “push” it away to ensure a clean separation and delivery of the medical device 12.

Illustrations in the above-described figures depict generally hollow or tubular structures 100, 200, 300, 500, 600 according to the present invention. When used herein, the terms “tubular” and “tube” are to be construed broadly and are not limited to a structure that is a right cylinder or strictly circumferential in cross-section or of a uniform cross-section throughout its length. For example, the tubular structure or system is generally illustrated as a substantially right cylindrical structure. However, the tubular system may have a tapered or curved outer surface without departing from the scope of the present invention.

FIG. 4 is a flow diagram including method steps for constructing or designing a delivery member such as the example delivery members described herein. Referring to the method 800 outlined in FIG. 4, in step 810, a first hypotube, a second hypotube, a flexible sleeve, a wire coil, and a stretch resistant member can be selected. The first hypotube can be a proximal hypotube 100 as described herein or as would otherwise be known to a person of ordinary skill in the art. The second hypotube can be a distal hypotube 300 as described herein or as would otherwise be known to a person of ordinary skill in the art. The flexible sleeve can be a sleeve or fused jacket 500 as described herein or as otherwise known to a person of ordinary skill in the art. The wire coil can include the support coil, coiled section 200 as described herein or as otherwise known to a person of ordinary skill in the art. The stretch resistant member can be a stretch resistant member 600 as described herein or as otherwise known to a person of ordinary skill in the art.

In step 820, the stretch resistant member can be positioned in the lumen of the wire coil. In step 820, the stretch resistant member that is positioned can be substantially tubular. In step 830, the first hypotube, wire coil, and second hypotube can be attached to each other. In step 840, the stretch resistant member is attached to the first hypotube and the second hypotube. The first hypotube, wire coil, and second hypotube can be attached as illustrated and described herein or by other means as would be understood by a person of ordinary skill in the art. Steps 820, 830, and 840 need not be performed in that order and can be performed simultaneously. For instance, the stretch resistant member can be attached to one of the first and second hypotubes as indicated in step 840, then the hypotube to which the stretch resistant member is attached can be attached to the wire coil as indicated in step 830, then the stretch resistant member can be positioned through the wire coil as indicated in step 820, then the other of the hypotubes can be attached to the wire coil as indicated in step 830, then the stretch resistant member can be attached to that other hypotube as indicated in step 840.

In step 850, the wire coil can be covered with the flexible sleeve. The flexible sleeve can cover some or all of the outer surface of the wire coil. Step 850 can also include the step of fusing the flexible sleeve to the wire coil and/or otherwise affixing the flexible sleeve to the delivery member. If the second hypotube has a flexible section, in step 850, the flexible sleeve can also be positioned to cover at least a portion of the flexible section.

In step 860, an implant can be detachably attached to the distal end of the first hypotube. In step 860, the implant can be attached by positioning a loop wire within the first hypotube, positioning a pull wire to extend through the first hypotube, coiled wire, and second hypotube, and securing the implant with the loop wire and the pull wire. The pull wire can be extended from the proximal end of the second hypotube. If the first hypotube has a compressible portion, in step 860, the compressible portion can be compressed, and the implant can be attached to delivery member while the compressible portion is compressed.

FIG. 5 is a flow diagram including method steps for administering an intravascular treatment using a system including a delivery member such as the example delivery members described herein. Referring to the method 900 outlined in FIG. 5, in step 910 a system having a distal hypotube, proximal hypotube, coiled section co-axially positioned in between the hypotubes, a flexible sleeve covering the coiled section, a stretch resistant member positioned within the coiled section, and a medical treatment device attached to or near the distal hypotube can be selected. The system can be suitable for intravascular treatments such as described and illustrated herein or as otherwise known to a person of ordinary skill in the art.

In step 920, the system can be moved through a catheter to a treatment site such as the site of an aneurysm or other abnormality in a blood vessel. In step 930, the system can be flexed as it is moved through the catheter. In step 940, the coiled section of the system can be prevented from deforming by the flexible sleeve and the stretch resistant member; the flexible sleeve can inhibit the coiled section from deforming radially while the stretch resistant member can inhibit the coil from extending longitudinally.

In step 950, the medical treatment device can be deployed. In the case that the medical treatment device is an implant, in step 950 the implant can be detached. In step 960, the distal tube can extend to push the medical treatment device away from the distal tube. In the case that the medical treatment device is an implant detached in step 950, in step 960, the detached implant can be ejected away from the distal tube in response to the expansion of the distal tube.

The descriptions contained herein are examples of embodiments of the invention and are not intended in any way to limit the scope of the invention. As described herein, the invention contemplates many variations and modifications of the delivery system, delivery member, and engagement system, including alternative configurations of components, alternative materials, alternative medical treatment devices, alternative means for deploying the medical treatment device, alternative geometries of individual components, alternative means for attaching component parts, etc. These modifications would be apparent to those having ordinary skill in the art to which this invention relates and are intended to be within the scope of the claims which follow. 

What is claimed is:
 1. A delivery member for delivering an implantable medical device to a target location of a body vessel, the delivery member comprising: a distal hypotube comprising a distal end shaped to receive the implantable medical device; a support coil section affixed to a proximal end of the distal hypotube; a proximal hypotube affixed to a proximal end of the support coil section; a lumen extending through the distal hypotube, the support coil section, and the proximal hypotube; a flexible sleeve covering at least a majority of an outer surface of the support coil section; and a stretch resistant member extending through a portion of the lumen, the stretch resistant member affixed to the proximal hypotube and affixed to the distal hypotube.
 2. The delivery member of claim 1, further comprising: an engagement system movable to engage and deploy the implantable medical device engaged at a distal end of the distal hypotube, the engagement system comprising: a loop wire extended through an opening in the implantable medical device thereby engaging the engagement system to the implantable medical device and movable to retract from the opening in the implantable medical device to deploy the implantable medical device, and a pull wire extended through the lumen, engaged to the loop wire thereby engaging the engagement system to the implantable medical device, and movable to retract proximally to disengage the loop wire to deploy the implantable medical device.
 3. The delivery member of claim 2, wherein the distal hypotube comprises a compressible portion movable from a compressed condition to an elongated condition, and wherein the engagement system maintains the compressible portion in the compressed condition when engaged to the implantable medical device.
 4. The delivery member of claim 1, wherein the support coil section comprises: a non-radiopaque proximal coil extending from the proximal end of the support coil section; a non-radiopaque distal coil extending from the distal end of the support coil section; and a radiopaque central coil extending between the non-radiopaque proximal coil and the non-radiopaque distal coil.
 5. The delivery member of claim 1, where in the support coil section comprises: a wire wound to form the support coil section and defining a portion of the lumen, the wire comprising a diameter measuring from about 0.0008 inch to about 0.005 inch.
 6. The delivery member of claim 1, wherein the flexible sleeve comprises a polymer, and wherein the flexible sleeve comprises additives effective to increase the lubricity of the polymer.
 7. The delivery member of claim 1, wherein the flexible sleeve is affixed to the proximal hypotube and the distal hypotube.
 8. The delivery member of claim 1, wherein the stretch resistant member is an extruded tube.
 9. The delivery member of claim 1, wherein the delivery member comprises a length measurable from the proximal end of the support coil section to the distal end of the distal hypotube, and wherein the length measures about 40 cm.
 10. The delivery member of claim 1, wherein the proximal hypotube comprises a spiral cut portion approximate a distal end of the proximal hypotube.
 11. A method of constructing a delivery member for delivering an implantable medical device, the method comprising: selecting a first hypotube comprising a first lumen therethrough; selecting a second hypotube comprising a second lumen therethrough; forming a wire coil section extending from a distal end of the second hypotube to a proximal end of the first hypotube such that the wire coil section defines a third lumen therethrough; extending a stretch resistant member through the third lumen; affixing the stretch resistant member to the first hypotube and second hypotube; selecting a flexible sleeve; covering at least a majority of the outer surface of the support coil section with the flexible sleeve; and detachably attaching the implantable medical device to the delivery member approximate a distal end of the first hypotube.
 12. The method of claim 11, wherein the step of forming the wire coil section further comprises: forming a non-radiopaque proximal coil extending distally from the distal end of the second hypotube; forming a non-radiopaque distal coil extending proximally from the proximal end of the first hypotube; and forming a radiopaque central coil extending between the non-radiopaque proximal coil and the non-radiopaque distal coil.
 13. The method of claim 11, wherein the step of forming the wire coil section further comprises: selecting a wire comprising a diameter measuring from about 0.0008 inch to about 0.005 inch; and winding the wire to form the wire coil section and define the lumen therethrough.
 14. The method of claim 11, wherein the step of selecting the flexible sleeve further comprises: selecting the flexible sleeve comprising a polymer and additives effective to increase the lubricity of the polymer.
 15. The method of claim 11, wherein the step of extending a stretch resistant member through the third lumen further comprises: extending the stretch resistant member that is substantially tubular through the third lumen.
 16. The method of claim 11, wherein the step of detachably attaching the implantable medical device to the delivery member approximate a distal end of the first hypotube further comprises: compressing the first hypotube; and detachably attaching the implantable medical device to the delivery member approximate the distal end of the compressed first hypotube.
 17. The method of claim 11, further comprising: positioning a loop wire within the first lumen; and positioning a pull wire to extend through the first lumen, third lumen, and first lumen, wherein the step of detachably attaching the implantable medical device to a distal end of the first hypotube further comprises: extending the loop wire through an opening in the implantable medical device; and engaging the pull wire to a portion of the loop wire extended through the opening in the implantable medical device.
 18. The method of claim 17, wherein the step of detachably attaching the implantable medical device to a distal end of the first hypotube further comprises: positioning the pull wire to extend proximally from a proximal end of the second hypotube. 